详细介绍C#数学运算表达式解释器的示例代码(2)-木庄网络博客

测试文件内容：

1 2	`a=2+32;` `b=2(2+3);`

浏览按钮事件处理程序：

 private void button_browse_Click(<a href="http://www.php.cn/wiki/60.html" target="_blank">object</a> s<a href="http://www.php.cn/wiki/1048.html" target="_blank">end</a>er, EventArgs e) { Open<a href="http://www.php.cn/wiki/1313.html" target="_blank">File</a>Dialog fbd = <a href="http://www.php.cn/wiki/165.html" target="_blank">new</a> OpenFileDialog(); fbd.Title = "请选择一个文件："; fbd.CheckFileExists = true; fbd.CheckPathExists = true; fbd.Filter = "*.txt(文本文件)|*.txt|*.*(所有文件)|*.*"; fbd.FileName = Environment.GetFolderPath(Environment.SpecialFolder.MyComputer); <a href="http://www.php.cn/wiki/109.html" target="_blank">if</a> (fbd.ShowDialog() == System.Windows.<a href="http://www.php.cn/wiki/125.html" target="_blank">For</a>ms.DialogResult.OK) { textBox_save<a href="http://www.php.cn/wiki/1275.html" target="_blank">Dir</a>.Text = fbd.FileName;  try { FileStream fs = new FileStream(fbd.FileName, FileMode.Open, FileAccess.Read); StreamReader sr = new StreamReader(fs); <a href="http://www.php.cn/wiki/121.html" target="_blank">while</a> (!sr.EndOfStream) { <a href="http://www.php.cn/wiki/57.html" target="_blank">string</a> line = sr.<a href="http://www.php.cn/wiki/691.html" target="_blank">ReadLine</a>(); analyse(line); } }  catch (<a href="http://www.php.cn/wiki/265.html" target="_blank">Exception</a> ex) { MessageBox.Show("错误：" + ex.Message + "\r\n堆栈：" + ex.StackTrace); } } } 

分析一行表达式：

private void analyse(string line)
{
    //以分号作为结束符，支持一行内写多个语句
    string[] expA = line.Split(new string[] { ";" }, StringSplitOptions.RemoveEmptyEntries);
    for (int i = 0; i < expA.Length; i++)
    {
        analyseExpA(expA[i]);
    }
}

计算一条表达式：

private void analyseExpA(string expA)
{
    string[] expB = expA.Split(new string[] { "=" }, StringSplitOptions.RemoveEmptyEntries);
    for (int i = 0; i < expB.Length; i++ )
    {
        Regex reg = new Regex("[a-zA-Z]");
        if (!reg.IsMatch(expB[i]))
        {
            object obj = EvalExpress(expB[i]);
            if (obj != null)
            {
                textBox1.Text += expA + " = " + obj.ToString() + "\r\n";
            }
            else
            {
                textBox1.Text += expA + ",无法识别的表达式\r\n";
            }
        }
    }
}